Diaphragm
Diaphragm is term used in physiology to describe several large muscle groups which are found only in humans and other mammals. These muscles are structural components that separate two adjacent regions of the body. Diaphragms in the human body include the pelvic diaphragm, the urogenital diaphragm, and the thoraco-abdominal diaphragm. The latter one, which is commonly referred to as "the" diaphragm, is the muscle that separates the chest cavity (which contains the heart and lungs), from the abdomen (which contains the stomach, intestines, and other organs.)
The term comes from the Greek word "diaphragma," meaning "barrier." The thoraco-abdominal diaphragm, which is located in the midriff, consists of muscle and membrane tissue and is attached to the rib cage. It has three openings for the esophagus, aorta, and vena cava. The muscle has a slightly concave structure and it arches over the liver on the right and the stomach on the left. When we breath in, a nerve center in the brain stem triggers the diaphragm to contract and pull downward. This motion also causes the ribs to move outward, which helps to expand the chest cavity. The resultant decrease in pressure causes air to be drawn into the lungs. When we breath out, we relax the muscle and it snaps back up into its previous position, contracting the chest and forcing air out of the lungs.
As the diaphragm moves up and down it also stimulates the stomach and liver and thus aids in digestion.
The diaphragm plays a critical role in the process of respiration and any interference with its free movement can prevent the proper intake of air into the lungs. Therefore, diseases which affect this muscle, such as poliomyelitis, seriously endangers life. Proper diaphragm function can also be impaired by developmental defects, hernia, injury, physical displacement, and infection. Minor perturbation of the diaphragm can cause a case of the hiccups, which occur when the diaphragm contracts with a series of quick spasms. These spasms make the diaphragm tighten suddenly, causing the lungs to draw in quick gulps of air. As this air rushes in, the vocal cords automatically close. As the air rushes by the vocal cords vibrate, creating the characteristic hiccup sound. Hiccups can be result from any irritation to the diaphragm that causes it to contract rapidly, such eating or drinking too fast. It can also be caused by muscle spasms that happen when the muscle is over exerted. After a few moments the diaphragm will usually relax and the hiccups will cease. Sometimes breaking the breathing cycle by taking a big drink of water, holding your breath, or breathing into a paper bag for a few minutes can also help. These tricks increase the amount of carbon dioxide in the lungs, which tends to slow or stop the muscle contractions.
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